The rain won’t relent today. A flash flood watch is in effect for all of Massachusetts until 8 p.m. and a flash flood warning has been issued until 3 p.m. for Suffolk County, Northern Norfolk County, and Southeastern Middlesex County. Temperatures will climb into the high 70s, with humid conditions lingering until the evening, according to the National Weather Service.

But “we won’t have this soupy moisture for much longer,” said Charlie Foley, a weather service meteorologist. “This evening and overnight a cold front is going to move across the state, and that’s going to introduce a drier, cooler air mass.”

Heavy showers and thunderstorms — and some tropical downpours — could bring 2 inches of rain to Boston early this afternoon, and some regions could see more.

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Heavy rain has already saturated the ground, heightening the chances for flash flooding of roads and streams. Franklin County had recorded more than 4 inches of rain by this morning, Foley said.

The chance of rain will diminish this evening. Temperatures will drop into the low 70s and dewpoints will remain in the upper 60s.

Wednesday will see temperatures in the mid-80s, with a mix of clouds and sunshine. The cold front will bring much more comfortable dewpoints, in the 50s. Scattered showers and thunderstorms are possible, and are most likely in Southeastern Massachusetts. Boston has a 20 percent chance of precipitation, according to the weather service.

Thursday and Friday will remain mostly dry and sunny. Humidity will be low and temperatures unlikely to break 80 degrees. Temperatures will rise a few degrees Saturday, but conditions will remain pleasant and seasonable.

Sunday could see some more precipitation that could bleed into Monday. Next week is likely to remain warm, but comfortable.

“We certainly won’t see the heat we saw in the recent past for next week,” Foley said, alluding to the recent seven-day heat wave, the third one this year.